/*
 * Copyright (c) 2004-2022, University of Oslo
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice, this
 * list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright notice,
 * this list of conditions and the following disclaimer in the documentation
 * and/or other materials provided with the distribution.
 *
 * 3. Neither the name of the copyright holder nor the names of its contributors 
 * may be used to endorse or promote products derived from this software without
 * specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
 * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
 * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
package org.hisp.dhis.commons.collection;

import java.util.ArrayList;
import java.util.Collection;
import java.util.List;

/**
 * List implementation that provides a paged view.
 *
 * @author Lars Helge Overland
 */
public class PaginatedList<T> extends ArrayList<T> {
  /** Determines if a de-serialized file is compatible with this class. */
  private static final long serialVersionUID = 6296545460322554660L;

  public static final int DEFAULT_PAGE_SIZE = 10;

  private int pageSize;

  private int fromIndex = 0;

  public PaginatedList(Collection<T> collection) {
    super(collection);
    this.pageSize = DEFAULT_PAGE_SIZE;
  }

  /**
   * Sets page size.
   *
   * @param pageSize the page size.
   * @return this PaginatedList.
   */
  public PaginatedList<T> setPageSize(int pageSize) {
    this.pageSize = pageSize;

    return this;
  }

  /**
   * Sets the number of pages. The page size will be calculated and set in order to provide the
   * appropriate total number of pages. The resulting number of pages can be lower than the given
   * argument but not higher.
   *
   * @param pages the number of pages.
   * @return this PaginatedList
   */
  public PaginatedList<T> setNumberOfPages(int pages) {
    this.pageSize = (int) Math.ceil((double) size() / pages);

    return this;
  }

  /**
   * Returns the next page in the list. The page size is defined by the argument given in the
   * constructor. If there is no more pages, null is returned. The returned page is not guaranteed
   * to have the same size as the page size.
   *
   * @return the next page.
   */
  public List<T> nextPage() {
    int size = size();

    if (fromIndex >= size) {
      return null;
    }

    int toIndex = Math.min((fromIndex + pageSize), size);

    List<T> page = subList(fromIndex, toIndex);

    fromIndex = toIndex;

    return page;
  }

  /** Sets the current page position to the first page. */
  public void reset() {
    fromIndex = 0;
  }

  /**
   * Returns the number of pages in the list.
   *
   * @return the number of pages.
   */
  public int pageCount() {
    int count = size();
    int pages = count / pageSize;
    int mod = count % pageSize;

    return mod == 0 ? pages : (pages + 1);
  }

  /**
   * Returns a list of all pages.
   *
   * @return a List of all pages.
   */
  public List<List<T>> getPages() {
    List<List<T>> pages = new ArrayList<>();

    List<T> page = null;

    while ((page = nextPage()) != null) {
      pages.add(page);
    }

    return pages;
  }
}
